I have enabled the enhanced multicore support - will see it that does the trick.

Am attempting to watch .mkv files appros 8gb inn size.

I could not see how to adjust the Java priorities - how do I do this?.

I am still not sure if any of my settings changes are actually happening though - I can select everything OK but, for example, I set the max bandwidth to 14 and the vidio quality setting to 'good for hd wireless' and the buffer to 600 but the buffer seems to stay at 400 and the peak bitrate is showing as 59506kb/s

as shagrath says, 1080p is not possible with wireless, because there's too much data to stream. with a resolution of 1920×1080, or 2,073,600 pixels, at let's say 30 fps, that's 60 M Pixels per second, even if that's 8 bits per pixel, it's too much for a 100 mega bit connection.